Method of fluid jet cutting for materials including rock and compositions containing rock aggregates

ABSTRACT

Materials including rock and compositions containing rock aggregates are subjected to a fluid jet cutting operation utilizing a first stage high-temperature, high-flux heat source and a second stage high-pressure hydraulic jet of water. The preferred heat source is a flame. In the first stage, the flame impinges upon a surface to be cut and material at the surface is rapidly heated by the flame to a state of massive incandescence. As heat penetrates and the heat front advances, there is also produced beneath the zone of incandescence a substrate of thermally fractured material. Fractures in the substrate define planes of weakness which extend generally parallel to the incandesced surface portions of the material. In the second stage of the fluid jet cutting method, a hydraulic jet of water of a diameter small in relation to the area of impingement of the flame is directed against the incandesced surface, preferably while the substrate is in a thermally activated state. The minute fluid jet stream when applied with its impact force suitably controlled is found to be capable of penetrating the thermally fractured substrate and reaching into the planes of weakness above indicated. Water thus injected into the substrate and moving along the planes of weakness almost instantly exerts a hydraulic pressure from within outwardly to remove substrate material in a novel manner.

PATENTDun: 5mn 3,704,914 sum 2 nf e RATE OF REMOVAL 0 20:00 40:00 lpecsuiolo 80'00 10,0'00 l v l I Iwe'or /uf @Maw @few Jima-2243.9

FIELD or THE INVENTION ries, mines, tunnels, excavations, masonry structures'.

and the like. c c

` DESCRIPTION OF THE PRIOR'ART Difficulties are presently encountered in cutting rock by conventional methods and equipment. Working rock with heat has been practiced for a long time and similarly, use of a flame'and a stream of water `has been disclosed in U.S. Pat.'No.165,6`77 issued .lune l1, 1867. The practice of working rock by means of hydraulic pressure is also well-known in the art. U.S. Pat. No. 2,675,993 issued to Smith et al. discloses a more efficient method of working rock utilizing a high-velocity, high-temperature flame jet to remove rock by the process commonly known as spalling. Here,'however, problems arise in using the flame jet due to the physical characteristics of rock and its component minerals and the manner in which it occurs in `a natural state. Generally speaking, flame jets work well in granite, a hard and mechanically strong rock; however, one of the minor common components of granite may be mica, a material which is relatively soft andresilient and which resists the flame jet action. It tends to'melt or at least soften beforespalling orflaking occurs and this impedes the thermal stressing and spalling action in a work area. A pocket of mica encountered by an advancing jet flame in granite may soften and even fuse,

retarding and perhaps stopping-the advance ofthe flame. Many other `minerals encountered in flame working rockbehave similarly.

Spalling of rocks such as granite which are normally highly spallable may be interrupted not only by softening an fusing, but also by the presence therein of cracks, fissures, partings and other discontinuities. These discontinuities are frequently present in rock formations which occur in layers or beds. Discontinuities may also develop due to earth pressure and other changes such as those resulting from thermal stress induced by conventional flame jet working.

These problems have been recognized in U.S. Pat. No. 2,675,933 where Smith et al. note that even highly spallable rocks tend to melt to some extent in a high temperature flame jet, and therefore, excessive heating is to be avoided, and where melting occurs or where seams or discontinuities are encountered, then according to Smith et al., it is necessary to penetrate the material mechanically. Because of these conditions, it will be appreciated that flame jets are ordinarily employed in the art in a manner such that incandescing and/or melting or fusing of the rock is avoided to the greatest extent possible. ln addition, thisprior art has two further disadvantages: creation of a high level of noise, and generation of air-home rock dust.

SUMMARY OFTHE INVENTION Itis, therefore, a chief object ofthe present invention to deal with the various problems indicated and to provide an improved method for flame cutting rock whereby substantial volumes of material may be removed efficiently, and interruption in progress of work due to incandescing, fusing, melting or the presence of discontinuities may be avoided.

With this general objective in mind, one form of the method which `I havedevised for fluid jet cutting employs a first stage hightemperature, high-velocity flame jet and a second stage high-pressure hydraulic jet of water in cooperating relationship. I make use of the high-temperature flame jet to carry out massive incandescing of rock unlike the conventional practice of Smith et al., U.S. Pat. No. 2,675,993 wherein heating to incandescence is avoided to the greatest extent possible. lncandescing the rock results in a relatively deep substrate of underlying material which is conditioned thereby for working by high-impact forces of the hydraulic jet.

This method is based upon a recognition of specific changes brought about by incandescence. lncandescing rock massively or in depth operates to form an outer surficial layer which is thermally degraded. More importantly, however,` incandescence results in the formation immediately below the surficial layer of a substrate which is characterized by a system of random fractures. The outer boundaries of these fractures, l have observed, define planes of weakness or separation in the case of some rocks extending substantially parallel to the surface which is incandesced. Although the thermally degraded layer and the fractured substrate are quite capable of resisting the scouring action and momentum of a conventional flame jet of high velocity, they,vnevertheless, are affected by forces of a higher order of magnitude such as the momentum of a water jet of suitably high impact force. l

In the first stage,l the flame jet is iimpinged upon a surface'to be cut and the initial thermal stress and momenturn of the flame jet operates to remove such spallable portions as may be present at the surface of the material. Non-spallable materials at the surface, or materials exposed by spalling, are rapidly heated by the flame jet, momentarily sustained, to a state of massive incandescence. As heat penetrates and the heat front advances, there is also produced beneath the zone of incandescence a relatively deep substrate of thermally stressed material. As a result of incandescence, the substrate, although not thermally degraded to the extend occurring at the surface, does become thermally frac tured with a system of random fractures developing and defining the planes of weakness above noted.

ln the second stage, a hydraulic jet of water of a diameter relatively small in relation to the area of impingement of the flame jet, is directed against a small area or spot in the incandesced surficial layer, preferably while the substrate is in a thermally stressed condition. The hydraulic jet exerts a high-impact force resulting from high velocity to provide a fine hydraulic stream which is capable of penetrating minute fissures or other discontinuities in the surficial layer and then moving inwardly into the substrate through the system of random fractures to find the planes of incipient separation extending generally parallel to the work surface as earlier described. Water thus injected exerts almost instantly a hydraulic pressure from within outwardly. Since the system of fractures induced in the thermally activated substrate by incandescing may be an area many times that of the vimpact spot of the hydraulic jet', there is exerted within the fractured substrate a total force many times that at the impingement spot of the jet. Thus the force at the impact spot of the jet and the hydraulic force acting from within outwardly operate as an unbalanced mechanical couple to provide a powerful wrenching force and to twist and tear away relatively large flakes and chips of the rock.

In combining the flame jet and hydraulic jet of the invention to form a substrate by incandescing and removing the substrate by hydraulic pressure, I find that l may further improve the art of flame working rock in another important aspect. l

In another form of my invention, I have discovered that I may heat some rock materials to a suitably incandesced state required for my hydraulic jet treatment by utilizing in place of vthe conventional high-velocity flame j'et of Smith et al., a suitably high-flux flame of relatively lower velocity which greatly reduces objectionable noise levels attendant upon the use of the flame jet of the Smith et al. patent, andI further find that the relatively low-velocity flame is capable of providing a heat flux of sufficient value to carry out a relatively rapid removal of the substrate material.

I have still further determined that I may employ my basic fluid cutting technique to carry out an improved method of rock channelling as practiced in granite quarries, for example, in the production of dimension stone, an art which is described in more detail in Vasselin U.S. Pat, No. 3,019,004. In my improved method, I am able to over come difficulties of a specific nature engendered by conditions encountered in a typical channelling operation. y

Also, l find that the hydraulic water jet of my invention alleviates the dust problem associated with the use of high velocity flames alone.

The nature of the invention and its other objects and novel features are further described in connection with the figures in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view illustrating a rock body frag mentarily and indicating diagrammatically the flame working step of the invention to provide incandescence.

FIG. 2 is a view similar to FIG. l showing the rock body viewed from another point of view and further indicating diagrammatically thermally degraded portions of the rock resulting from flame working.

FIG. 3 isanother diagrammatic view similar to FIG. 2 but further indicating the application of a hydraulic jet of water to the incandesced surface of rock.

FIG. 4 is still another view similar to FIGS. 2 and 3 and further indicating diagrammatically removal of fractured material by means of the hydraulic jet.

FIG. 5 is an enlarged fragmentary view of a rock mass illustrating diagrammatically a water jet Aapplied to an incandesced surface of the rock and further showing schematically movement of water from the water jet into a thermally fractured region of the rock below its surface.

FIG. 6 is a graph illustrating relative performance of the method of the invention.

FIG. 7 is a fragmentary plan view of a rock body illustrating diagrammatically a flame and an incandesced region produced by the flame and also indicating the point of impingement of a hydraulic jet in the flame area.

FIG. 8 is a detail viewillustrating portions ofa rock body and a hydraulic jet impinging thereagainst.

FIG. 9 is a diagrammatic view illustrating a mass of rock being formed with a channel and indicating means for positioning and applying a flame jet and a hydraulic jet in cooperating relationship.

FIGS. 10 and 1l aredetailed elevational hydraulic jet means employed in channelling.

FIGS. 12 to 19, inclusive, are Schematic views illustrating channelling procedures and thermal gradients associated therewith.

FIG. 20 is another diagrammatic view of another form of flame employed in combination with a hydraulic water jet.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In carrying out the method of the invention, an important'feature consists in heating the rock to incandescence to provide thermal stressing which extends into the rock well beyond the surface region along which conventional spalling may occur in the case of a spallable, rock. For this purpose, I may employ any suitable heat source and one preferred heat source comprises a flame jet emitted at high velocity from an internal burner and having a flame temperature in excess of 2,500 F. A flame jet of this class has heat flux characteristics, i.e., BTU emitted per minute per square inch of flame orifice, adequate to accomplish rapid thermal stressing of the type necessary in producing a system of fractures in a substrate of rock. The high temperature of the flame and the high heat flux to the rock surface creates initially an extremely steep temperature gradient between the surface material and that which is beneath, and spalling may occur where spallable material is present. The upper limit of this steep gradient generally is below the temperature of incandescence when progressive spalling occurs. If spalling stops, continued application of'heat by the flame causes static degradation of surface portions of the material, and the upper limit of the gradient rises to a value above the temperature of incandescence and heat front advances into the rock in depth with the thermal gradient becoming less steep.

With respect to difficulty spallable rock surface material, flakes may form at the surface and be stripped away by the flame jet. Other flakes may partially form but not be dislodged and-as heating continues, temperature rises rapidly and the rock becomes incandescent. Heat penetrates in depth and creates in the rock a volume of degraded rock of increasing thickness as the heat front advances to produce a fractured substrate which is characterized by random fracture planes, some of which are generally parallel to the work surface.

views of 4layer 8 of relatively high-temperature thermal degradation. Formation of layer 8 results from a high temperature heating andthe associated extremely steep'thermal gradient. Below the surficial layer 8, thereA is formed concurrently a substrate of fractured material which results from lower temperature heating and a thermal gradient which is less steep. t

In this first stage of fluid jet cutting of the invention as illustrated in FIGS. l and 2 in which the` substrate of fractured material l0 isformed below the incandesced surface 8 of the rock, the heat front which advances inwardly and induces fracturing of material causes the formation of planes of weaknesssome of which extend generally parallel to the incandesced surface. In FIG. 2,

the planes of separation are indicated along irregular lines and the planes are denoted by the arrows P.

It is pointed out that as a result of an exceedingly steep gradient being created at the surface of the rock and a gradient of lesser steepness being created well within the surface, thermal degradation of varying character is induced. Thus at the surficial layer 8, there may be induced, depending upon the nature of the rock, rapid spalling or spalling with difficulty or no spalling at all. There may develop fusing or meltingfof rock components, or decomposition may take place with water of crystalization and water of hydration being driven off and with voids or fissures being formed, or the surface may shrink or expand to a much greater degree than underlying portions.

Where a thermal gradient of progressively lesser steepness is created well within the incandesced surface, a less severe degradationtakes place and `thus fractures are induced to constitute regions of incipient separation and innermost boundaries of these fractures thus define the planes of weakness above referred to as illustrated diagrammatically on a larger scale in FIG. 5 where in the planes are indicated by arrow P. I find that some of the planes of weakness thus formed may extend generally parallel to the surface of the rock and separate quite sharply thermally stressed rock from adjacent strong undegraded rock portions indicated at numeral l2. In FIG. 5 a fracture line is shownonan exaggerated scale and denoted by a reference character The second stage of fluid jet cutting of the invention is illustrated diagrammatically in FIGS. 3 an'd4 and also4 in FIG. 7. In this second stage of cutting, a minute high-velocity hydraulic jet of water 14 is directed against a smallarea or spot on the incandesced rock 2 with its surficial layer 8 of static thermal degradation and the substrate of fractured material 10 as shown in FIG. 3. In most instances of cutting, the hydraulic jet 14 is applied within a short interval of time after incandescing has been carried out and in one preferred embodiment ofthe method, the hydraulic jet 14 is employed while thesubstrate is in a thermally activated state in which fracturing or other changes are still in effect in the mass. The interval occurring between incandescing and applying the jet may, however, vary considerably depending on the nature of the specific rock which is to be cut and other conditions or requirements involved in the particular type lof cutting operation desired. j

The minute high-velocity hydraulic jet is maintained against the small area or spot of impact for the short interval noted andthen the fractured material begins to break away and become displaced away from the surface as suggested diagrammatically by the relatively large flakes 16, 18, 20 etc. t in FIG. 4, and there is produced a cut having a depth, for example a-a (FIG. 4) which is appreciably greater than the depth obtained in a cut carried out by conventional spalling. It will be understood that progressive cutting is realized by moving the heat source to incandesce an adjacent area of `the rock and repeating the fluid jet working above described.

An important feature of my second-stage of cutting consists in providing a hydraulic jet of water 14, which is of a very small diameter relative to the incandesced area D produced by flame 6a, as shown diagrammatically in FIG. 7 and which is capable of passing through the surficial layer 8 and penetrating the thermally fractured substrate l0 along the fractures as suggested by the fracture line F indicated diagrammatically in FIG. 5. In thus providing a jet of water which is capable of penetrating the surficial layer and the fractured substrate as well as overcoming cohesive forces of the rock at the fracturelines, I have discovered that by providing a hydraulic jet of water or other suitable liquid having a very high pressure and a very small or minute diameter and by maintaining the jet against a small spot or impingement for a short interval, the fractured substrate is not 4only pierced by the jet, but more importantly, water is forced between some of the fractured portions to open these fractured portions as suggested diagrammatically in FIG. 5 by the dotted lines F1. Water thus entering the surficial layer 8 as by means of the tiny fissure F2 and introduced between the fracture portions F and F1 move along the planes of weakness P as indicated by the small directional arrows, and the water `rapidly exerts hydraulic pressure. The pressure developed within the confines of the fracture system which the jet water has entered approaches the-level of the stagnation pressure of the jet itself. This hydraulic pressure acts against a relatively large area from within outwardly to open the planes of weakness P as suggested by the dotted line P1. Portions of rock thus separated from the strong rock mass 12 are almost instantly wrenched and twisted away from the strong rock mass 12 and become hydraulically expelled in the form of relatively large flakes, any one of which may include a number of fracture portions.

As illustrative of a workable jet size for jet pressure which is capable of penetrating an incandesced rock with a fractured substrate, I have determined that in one desirable form the water jet may be projected from a nozzle having a diameter of 0.055 inches by means of a pump capable of developing a jet pressure in a range of from 2,000 to 10,000 p.s.i. I find that no appreciable removal of material takes place with jet pressure in the range up to l,000 p.s.i. However, at yhigher pressure levels, a very small rate of removal is observedup to 2,000 p.s.i. And above this level, a definite increase takes place with significant cutting being realized at about 4,000 p.s.i., and with best results being obtained above 6,000 p.s.i. These results are illustrated diagrammatically in the graph of FIG. 6 where relative rate of removal is plotted against water pressure values.

lt will be noted that the water jet orifice size of this invention is kept extremely small, particularly in relation to the flame orifice of the conventional flame jet y tool. At the very high hydraulic pressures required, and

with the very high water jet velocities which result, a very small orifice will deliver tremendous power.

With a water jet of 0.055 inches diameter angularly directed against a surface of incandesced rock and under a pressure in a range of from 4,000 to 6,000 p.s.i., it has been observed that the jet after a short in terval penetrates the surface of the degraded rock and enters fractured material beneath the surface and water is seen to emerge at points spaced from the point of impingement and flakes are removed in a mass of several square inches in area and having, for example, a thickness of one-fourth inch.

It is believed that the hydraulic action realized may be likened to the effect of an unbalanced mechanical couple in a manner more fully described below in connection with FIG. 8. The pressure of the jet 14 at its point of impingement with the incandesced surface 8 is applied in the direction of the jet axis at one small point. Outward hydraulic force is exerted within planes of separation or weakness which may be both of substantial area and at random locations a considerably distance from the spot of jet impact, and this force acts from within outwardly as suggested by the arrow C. The two forces described in combination provide a powerful wrenching and twisting action to tear flakes of material free from mechanically strong rock. This remarkable mechanical effect depends on the use of a jet of small area relative to the areas of weakness in the fractured material, since pressure appliedover a large area would be in a direction to tend to hold the weakened portions against one another ,instead of separating them.

lt should be understood that few varieties of rock are sufficiently spallable to be successfully worked with conventional flame jets. In spallable rocks, troublesome incandescence generally occurs as a reflection of the fractures and concentrations of fusible minerals which may be encountered. Such incandescence occurs intermittently. The capacity of the hydraulic jet of the second stage of my invention to remove the thermally degraded portions beneath the incandesced surface is of special interest in regard to rocks which incandesce continuously when worked by conventional flame jets alone without continuous removal of degraded portions. Such rocks are generally not worked with flame jets because continuous cutting cannot be attained due to the failure of the high velocity gases to remove the thermally degraded rock. However, l find that a high velocity water jet will deal with steady state incandescence by continuously removing thermally degraded portions. Thus, it is an important attribute of thi's invention that it extends the art of thermal cutting to classes of rock not presently worked with conventional flame jets.

As a specific example of a mode of practice of this invention, there may be cited its use in carrying out a channelling operation in a dimension stone quarry. Channels, relatively narrow, long and deep slots, are customarily cut into the ledge in the production of such stone, as a primary operation in the production of quarry blocks, which may subsequently be milled into building stone, monument stone, or whatever other form of dimension stone may be required. In dimension granite quarrying, such channels are approximately 3 inches to 5 inches in width, and a great many feet in length and depth.

A view of such an operation is indicated in FIG. 9 wherein a channel 46 is being cut into the ledge 45. The flame jet 41 impinges the end wall of the channel to be advanced, being emitted from the burner 40 at the end of the burner nozzle. The burnerv is supplied with fuel, oxidant, and coolant through the three corresponding hoses 37, 38 and 39 which lead from the flame control panel 36. The high pressure water jet 42 is emitted from the nozzle at the end of the hydraulic support pipe 35 fed by the hydraulic supply hose 34. This hose 34 conducts the water at high pressure from the pump 31 which is driven by the motor 32 and supplied with water at ordinary pressures through the hose 33.

It will be noted that the two jet support pipes 35 and 40 are supported in secured relation to each other by the clamps 40a and 40b, so that they may be manipulated as a unit, and raised and lowered in the channel by the support cable 44 which suspends them from the winch stand 43.

It should also be noted that the clamps 40a and 40b may provide for rigid connection of the support pipe 35 and 40, or may allow for rotating or sliding adjustment of one to the other. Also, the clamps 40a and 40b may be omitted,l so that the two support tubes are independent, and free to be manipulated selectively by the operator.

In the manipulation of the hydraulic jet of this invention, its high reaction thrustmay present a problem, particularly when working in a deep channel. Where it is desired that the hydraulic jet be projected vertically downward, then the arrangement shown in FIG. 11 is convenient, where the jet 42 is projected in a direction axial to the support tube 35, and the jet thrust thereby reacts against the weight of the tube. Where it is desirable that the jet be directed at an angle to the axis of the tube, and this may be when working a vertical end wall of a channel, then the arrangement shown in FIG. 10 may be preferred. In this figure the support tube '35 is provided with two jet orifices, so that the jet 42 is projected at an angle oblique to the tube axis, and an opposing jet 42A is projected at a right angle. The thrust of each jet tends to balance that of the other. Either one of the jets may be used as the working jet of the invention.

The method of practice of the invention as exemplified by channelling in a dimension granite quarry is to remove masses of rock from the narrow end wall of the channel in successive up and down passes. As shown in FIG. 9, the equipment may be provided with suspension and raising and lowering means. Conventionally the operator works from a position above the channel, where he may observe the conditions at the work face, and the removal of rock material as it falls to the channel floor. As various conditions may develop,

he manipulates the equipment to bring the flame jet and water jet to `bear in the manner best suited to rapid progress of the work.

Four conditions may be cited as representative of the manner of practicing this invention in the advancing of a channel in granite. These four conditions are represented in FIGS. 12, 14, 16 and 18, which present enlarged horizontal sections taken through the end wall of the advancing channel 46 in the ledge 45.`FIGS. 13, l5, 17 and 19 present corresponding graphs of the temperature gradient which occurs in the rock as the work face advances. These graphs are drawn with the distance into the rock being represented by the abscissae'axis, and the temperature being represented on the ordinates. In each figure the dashed line represents the temperature of incandescence.

FIG. 12 represents the condition where continuous spalling occurs under the flame action. Spall removal advances at a rate which maintains a steep gradient at the face below the temperature of incandescence.

FIGS. 14 and 15 present the condition where the work face approaches a pre-existing discontinuity shown as a fracture 60 in the rock. Many rock bodies contain such fractures, and the condition is therefore fairly common. Such a fracture presents a mechanical and thermal discontinuity. The mechanical effect is to impair the tendency to spalling. The work surface temperature increases under the heat of the flame, and it becomes incandescent. The heat penetrates the surface in depth. However, the preexisting fracture constitutes a thermal barrier for heat penetration, preventing the establishment of a smooth temperature gradient. A heat build up occurs between the zone of incandescence and the barrier. Rapid thermal degradation of the entire mass of rock between the work face and the fracture occurs. It is thereby rapidly conditioned for the action of the water jet. Hydraulic penetration is favored by the high'degree of degradation between the fracture and the work face, and commonly the fracture itself becomes the plane of separation under the hydraulic action. I

Another condition which occurs in channelling a granite ledge is that deeppartal fracturing occurs in the course of the work in the zone adjacent to the work face. This fracturing may be caused by the presence in the granite mass of high natural compressive earth stresses. FIG. 16 indicates such a fracture 61, which may be one of a system of such fractures 61A. As suggested in the figure such stress-induced fractures tend to run generally parallel to each other, and commonly occur in a direction oblique to the advancing channel. When this type of fracturing occurs it is particularly troublesome to the conventional art of channelling by flame alone, and undesirably wide and irregular channels may result. As such fractures occur, the thermal laction is quite similar to that which occurs when a preexisting fracture is encountered, as shown in FIG. 17. The stress field is disturbed, the work face becomes incandescent, the fracture 61 becomes a barrier to heat penetration, and the rock material between the fracture and the work face becomes highly degraded as its temperature increases.

A fourth condition which occurs is that there is frequently encountered a localized zone of some mineral which tends to fuse under the heat of the flame. The mineral mica may have this behavior. In FIG. 18 a pocket of such mineral is indicated at 62, the surface portion 63 of which has become fused. Spalling cases, and as indicated in FIG 19, the surface temperature reaches that of incandescence. Heat penetrates the mass, the temperature gradient flattens, and a deep degradementzone results. Where the temperature is high, but not high enough to cause-` fusion, the degradement is in the form of particulate fracturing well suited to the hydraulic action of the water jet.

It may be noted thateach of the three previously described'cohditons represented by FIGS. 14 19 which are particularly troublesome to the conventional art of flame Spalling, are thereby particularly suited to the technique of this invention, in that they favor development of a surface incandescent condition and the degradation of the underlying substrate by the development of a high temperature condition in that substrate. It is believed that high substrate temperature favors fracturing and weakening of the substrate. Therefore high substrate temperature favors removal by the subsequent hydraulic action. Although the conditions have been described as they occur in channelling, they also occur in rock cutting for other purposes.

The above conditions are not only troublesome to the prior art in that the rate of progress is impeded, but also in that the longer dwell-time of the flame at the trouble spot may undesirably enlarge the channel laterally and cause irregular and recessed channel side walls. The speed with which the hydraulic jet of this invention removes the deep thermally degraded substrate which results from these conditions permits the operator to advance the channel rapidly and assists him in maintaining `desirable parallel walls, and controlled channel width.

It is to be emphasized that the particular effectiveness of the hydraulic `stage of this invention is due to the relatively small area of impact of the jet, and to the unbalanced mechanical couple which results as the substrate planes of weakness become charged with the hydraulic pressure. As earlier noted in connection with FIG. 8, forces are exerted by a water jet such as the water jet 14 of FIG. 8 or the water jet 42 of FIG. 9, and impace forces are exerted over a yrelatively small area of impingement. For example, a jet 0.055 inches in diameter has an impact area of less than l/400 of a square inch. The direction of the impact forces is indicated by the arrow E in FIG. 8, vbeing not necessarily normal to the rock surface. As the jet penetrates to find the planes of weakness in the substrate, indicated at P in FIGS. 2, 3 and S, it develops a hydraulic pressure from within outwardly as earlier noted by the arrow C in FIG. 8. Also, it may be re-emphasized that the area of the substrate plane is larger 'than the area of jet impingement by several orders of magnitude as indicated in FIG. 7 Thus high disruptive force may be generated and a large mass wrenched free by the unbalanced mechanical couple of forces.

Still another important application of my two-stage jet cutting technique is found to be its use in ldealing with the high noise level conditions of a conventional flame cutting operation where a lnoise level in a magnitude of from to 130 decibels may be present.

With the use of equipment involving high noise levels, a highly desirable objective, as earlier noted, is reduction in this noise level and this I find can be accomplished in a highly practical manner by carrying out incandescence and thermal fracturing with a flame whose temperature and heat flux characteristics are adequate but whose flame velocity is substantially lowered with the RESULT that its noise level is greatly reduced. It is to be noted that the low velocity flame to be employed in accordance with my invention may not be at all effective used alone in flame cutting rock in the conventional manner and the reason for this is that the low velocity flame does not generate sufficient momentum to provide a scouring action which can remove spalled or partially spalled rock particles.

In FIG. 20, I have illustrated a low velocity flame L and a water jet J directed against a rock surface S. The low velocity flame has characteristics as noted below and is capable of operating within the decibel range also noted below.

The type of low-velocity flame shown in FIG. is that typified by the well-known Oxy-acetylene flame, in which the fuel and oxygen are burned externally of the burner, as distinguished from the high-velocity jet in which the fuel and oxygen are burned under pressure in a combustion chambered and the products of combustion are caused to issue through an orifice where a part of the potential energy is converted to kinetic energy. By contrast, the flame resulting from external combustion of fuel and oxygen is of relatively low velocity, always considerably lower than sonic velocity, and frequently lower than 500 feet per second, at which velocities the kinetic energy is usually insufficient for the scouring action that is necessary to cause spalling.

Such a low-velocity flame is sometimes referred to as an open flame, to distinguish from the closed-chamber combustion of the high-velocity jet system. The rockspalling characteristics of various flames are shown in the graphs of FIG. 9 of the Browning U.S. Pat-No. 3,103,251, from which appears that an open flame (designated welding torch in the graph) has little effect by itself alone in causing rock removal by spalling, even though its heat flux may e fairly high.

Nevertheless, the open flame has an important advantage in diminution of noise. Such flames may operate well below 80 decibels. The conventional jet obtained by closed-chamber combustion results in velocities approaching sonic, and in some instances the velocities extend into the supersonic range, causing excessive noise.

In instances where the objectionable features of high-energy jets cannot be tolerated, the present invention contemplates the use of a flame of low kinetic energy, which by itself would be inefficient for rock removal, in combination with a fine high-velocity water jet of the character previously described herein. The mechanism of operation is believed to be similar to that of the combination of the high-energy thermal jet with the water jet, in that incandescence from the flame prepares the crevices or fissures for penetration of the fine stream of water, which then serves to tear or wrench the spalls or flakes of rock from the mass. However, the open flame system is distinguished by the method whereby the rock, even though of a character which would be spallable (without incandescing) under the action of a high-velocity flame, is brought to a state of incandescence and surficial thermaldegradation with an underlying substrate of random fractures, following which the fine highvelocity stream of water is directed against the surface to penetrate the frac tured volumes in a manner to exert hydraulic pressure from within outwardly to tear or wrench flakes or layers from the mass.

Thus it will be apparent that I have disclosed improved methods of cutting rock by means of which it becomes possible to cut some rocks which cannot otherwise be dealt with and in other cases the rate of cutting spallable rock may be improved and various operating advantages realized.

I claim:

1. In a method of cutting materials including rock and compositions containing rock aggregates, the steps which include providing a flow of heat into a surface area of the material to be cut by means of a high-temperature heating source for a momentarily sustained period to form a volume of incandescent material which is characterized by a surface layer of thermal degradation and an underlying substrate of random fractures defining planes of weakness extending generally parallel to the incandesced surface,- directing against said surface layer a hydraulic jet of water under a pressure of at least 2,000 p.s.i. and at an angle at which the jet penetrates the thermally fractured substrate and maintaining the jet against said surface layer for a short interval to force water through the random fractures and along the planes of weakness extending generally parallel to the surface of the incandesced material thereby to exert hydraulic pressure in progressively increasing areas from within outwardly and to remove flakes or layers of material defined by the planes of weakness.

2. A method according to claim 1 in which the hydraulic jet is applied while the rock is in a thermally activated state.

3. A method according to claim l in which the hydraulic jet is supported in an angularly disposed position relative to the surface layer whereby the impact force of the jet of water and the said hydraulic forces exerted from within outwardly operate as an unbalanced mechanical couple to remove substrate material.

4. A method according to claim 1 in which the surface is heated to a state of thermal degradation by a low-velocity flame which by itself alone is incapable of causing appreciable progressive spalling.

5. A method according to claim 1 in which the rock contains material which is fused under heat in a manner to prevent spalling under the action of the flame jet, and the water jet penetrates said fused portions to exert hydraulic pressure outwardly from within the rock.

6, A method according to claim 1 in which the surface is heated to a state of thermal degradation by an open flame.

7. A method according to claim 1 in which the surface is heated to a state of thermal degradation by an open flame operating at a noise level below decibels and having a velocity substantially less' than sonic velocity.

8. In a method of cutting a material of the class including rocks and materials containing rock ag gregates, the steps which comprise applying against the outer surface layer of the material a flame jet momentarily sustained to heat said surface layer to a state of massive incandescence thereby to form a substrate of fractured material characterized by planes of weakness which extend generally parallel to the incandesced surface portions, directing ahydraulic jet of water under a pressure ranging from 2,000 to 10,000 p.s.i. against a small area of said incandesced surface layer, said jet having a high impact force 'to penetrate the thermally fractured substrate, maintaining the hydraulic jet to force water through the substrate and then along the planes of weakness in directions generally parallel to and below the incandesced layer to exert hydraulic pressure of constantly increased magnitude from within outwardly to provide rapid removal of material.

9. A method according to claim 8 in which the hydraulic jet is supported in an angularly disposed position relative to the surface layer whereby the impact force of the jet of water and the said hydraulic forces exerted from within outwardly operate as an unbalanced mechanical couple to remove substrate material,

l0. method according to claim 8 in which the hydraulic jet is applied while the rock is in a thermally activated state. l

l1. In a method of cutting a material of the class including rock and materials containing rock aggregates, the steps which comprise applying a flame jet against an outer surface of the material to heat the surface to an incandescent state and to form a substrate of thermally fractured material defining a plane of weakness extending generally parallel to to the said incandesced surface, applying a hydraulic jet of water whose diameter and impact force are suitably controlled to penetrate the thermally fractured substrate and maintaining the hydraulic jet of water to force water along the planes of weakness and to exert hydraulic pressure for expelling substrate material.

12. A methodaccording to claim 11 in which a discontinuity in the rock bars heat penetration, and a high temperature condition is developed inthe mass between the work face and the barrier to create a deep fractured substrate.

13. A method according to claim 11 in which the surface area of the material consists in the vertical end face of a channel and the high-temperature heating source and hydraulic jet cooperate to extend the sides of the channel along substantially parallel planes.

14. In a method of cutting rock and materials containing rock aggregates, the steps which comprise:

a. applying against an outer surface of the material a high-temperature flame jet to produce in the area of impingement of the flame jet thermally degraded portions in which heat penetrates in depth and creates a volume of thermally fractured material;

b. then directing a minute hydraulic jet of water under a pressure ranging from 2,000 to 10,000 p.s.i. against al spot in the said area of flame impingement to force the water into the thermally fractured volume; and c. maintaining the hydraulic Jet against the spot for a sufficient interval to exert hydraulic forces from deep within the volume of thermally fractured material outwardly by pressure of water penetrating through minute fissures forming in the fractured material, thereby to provide for removal of substantial quantities of said material.

15. A method according to claim 14 in which the high-pressure water jet is applied while the rock is in a thermally activated state.

16. A method according to claim 14 in which the flame jet is applied for a period during which the said material reaches a state of massive incandescence.

17. A method according to claim 1S in which the outer surface of the material undergoes spalling and portions uncovered by spalling are heated to a state of incandescence. 

1. In a method of cutting materials including rock and compositions containing rock aggregates, the steps which include providing a flow of heat into a surface area of the material to be cut by means of a high-temperature heating source for a momentarily sustained period to form a volume of incandesCent material which is characterized by a surface layer of thermal degradation and an underlying substrate of random fractures defining planes of weakness extending generally parallel to the incandesced surface, directing against said surface layer a hydraulic jet of water under a pressure of at least 2,000 p.s.i. and at an angle at which the jet penetrates the thermally fractured substrate and maintaining the jet against said surface layer for a short interval to force water through the random fractures and along the planes of weakness extending generally parallel to the surface of the incandesced material thereby to exert hydraulic pressure in progressively increasing areas from within outwardly and to remove flakes or layers of material defined by the planes of weakness.
 2. A method according to claim 1 in which the hydraulic jet is applied while the rock is in a thermally activated state.
 3. A method according to claim 1 in which the hydraulic jet is supported in an angularly disposed position relative to the surface layer whereby the impact force of the jet of water and the said hydraulic forces exerted from within outwardly operate as an unbalanced mechanical couple to remove substrate material.
 4. A method according to claim 1 in which the surface is heated to a state of thermal degradation by a low-velocity flame which by itself alone is incapable of causing appreciable progressive spalling.
 5. A method according to claim 1 in which the rock contains material which is fused under heat in a manner to prevent spalling under the action of the flame jet, and the water jet penetrates said fused portions to exert hydraulic pressure outwardly from within the rock.
 6. A method according to claim 1 in which the surface is heated to a state of thermal degradation by an open flame.
 7. A method according to claim 1 in which the surface is heated to a state of thermal degradation by an open flame operating at a noise level below 80 decibels and having a velocity substantially less than sonic velocity.
 8. In a method of cutting a material of the class including rocks and materials containing rock aggregates, the steps which comprise applying against the outer surface layer of the material a flame jet momentarily sustained to heat said surface layer to a state of massive incandescence thereby to form a substrate of fractured material characterized by planes of weakness which extend generally parallel to the incandesced surface portions, directing a hydraulic jet of water under a pressure ranging from 2,000 to 10,000 p.s.i. against a small area of said incandesced surface layer, said jet having a high impact force to penetrate the thermally fractured substrate, maintaining the hydraulic jet to force water through the substrate and then along the planes of weakness in directions generally parallel to and below the incandesced layer to exert hydraulic pressure of constantly increased magnitude from within outwardly to provide rapid removal of material.
 9. A method according to claim 8 in which the hydraulic jet is supported in an angularly disposed position relative to the surface layer whereby the impact force of the jet of water and the said hydraulic forces exerted from within outwardly operate as an unbalanced mechanical couple to remove substrate material.
 10. method according to claim 8 in which the hydraulic jet is applied while the rock is in a thermally activated state.
 11. In a method of cutting a material of the class including rock and materials containing rock aggregates, the steps which comprise applying a flame jet against an outer surface of the material to heat the surface to an incandescent state and to form a substrate of thermally fractured material defining a plane of weakness extending generally parallel to to the said incandesced surface, applying a hydraulic jet of water whose diameter and impact force are suitably controlled to penetrate the thermally fractured substrate and maintaining the hydraulic jEt of water to force water along the planes of weakness and to exert hydraulic pressure for expelling substrate material.
 12. A method according to claim 11 in which a discontinuity in the rock bars heat penetration, and a high temperature condition is developed in the mass between the work face and the barrier to create a deep fractured substrate.
 13. A method according to claim 11 in which the surface area of the material consists in the vertical end face of a channel and the high-temperature heating source and hydraulic jet cooperate to extend the sides of the channel along substantially parallel planes.
 14. In a method of cutting rock and materials containing rock aggregates, the steps which comprise: a. applying against an outer surface of the material a high-temperature flame jet to produce in the area of impingement of the flame jet thermally degraded portions in which heat penetrates in depth and creates a volume of thermally fractured material; b. then directing a minute hydraulic jet of water under a pressure ranging from 2,000 to 10,000 p.s.i. against a spot in the said area of flame impingement to force the water into the thermally fractured volume; and c. maintaining the hydraulic jet against the spot for a sufficient interval to exert hydraulic forces from deep within the volume of thermally fractured material outwardly by pressure of water penetrating through minute fissures forming in the fractured material, thereby to provide for removal of substantial quantities of said material.
 15. A method according to claim 14 in which the high-pressure water jet is applied while the rock is in a thermally activated state.
 16. A method according to claim 14 in which the flame jet is applied for a period during which the said material reaches a state of massive incandescence.
 17. A method according to claim 15 in which the outer surface of the material undergoes spalling and portions uncovered by spalling are heated to a state of incandescence. 